Precipitation hardenable copper, nickel, aluminum, zirconium alloys



United States Patet PRECIPITATION HARDENABLE COPPER, NICKEL, ALUMINUM,ZIRCONIUM ALLOYS John S. Roberts III, Fairfax, Va.

No Drawing. Application December 22, 1954, Serial No. 477,130

6. Claims. (Cl. 75-159) This invention relates to alloys and is moreparticularly concerned with alloys having properties comparable to thoseof copper-beryllium alloys but which do not employ any beryllium.

Copper-beryllium alloys are very important industrially and for militarypurposes. Because of their non-magnetic properties, good electricalconductivity, high tensile strength, high degree of hardness, and theirability to be cast, wrought, forged or drawn, they have been founduseful for many purposes, including various types of surgicalinstruments, electrical contact points, coil springs, cutting tools ofvarious kinds, including non-magnetic knives for underwater navaloperations, etc.

However, beryllium is one of the rare elements of the earths crust andis not available in suflicient quantities to permit its wide use as analloy element. Moreover, its indicated use in the field of atomic energyhas rendered its supply for other purposes even scarcer. The cost ofthis element is also very high which is another serious deterrent to itsgeneral use as an alloying element.

Accordingly, one of the objects of this invention is the provision of aberylliumefree copper alloy having physical properties similar to thoseof copper-beryllium alloys.

Another object of the invention is the provision of such aberyllium-free alloy which contains relatively inexpensive alloyelements.

A further object of the invention is the provision of such aberyllium-free alloy which contains elements in substitution of theberyllium which are relatively abundant.

A still further object is the provision of an alloy of the typementioned in which the tensile strength and hardness can be greatlyincreased by relatively short heat treatments or cold working treatmentsor both.

These and other objects and advantages of the invention will appear morefully from the following description.

The beryllium-free alloy in accordance with this invention comprisesessentially, copper, nickel, aluminum and zirconium in the approximateratio of one part nickel to about 10 parts copper and fractional partsof both zirconium and aluminum. The alloy may also contain fractionalparts of iron, silicon and carbon. The following percentages by weightare found to give generally satisfactory results:

Copper 82.2 to 89.1 Nickel 7.5 to 8.9 Aluminum 0.8 to 3.4 Zirconium 0.5to 4.0 Iron 0.7 to 1.3 Silicon 1.0 to 1.6 Carbon 0.05 to 0.5

The alloy is a liquid at about 1085 C. and can be cast in molds andwrought to finished forms as in the case of fabricating copper-berylliumalloys. After casting, it is given the usual solid solution treatment byelevating the temperature to a point below the melting point ICC whereelements of the alloy are in solid solution and then quenching in water.The tensile strength and hardness of the alloy at this point can beincreased to a remarkable extent by precipitation ageing and coldworking and, moreover, the ageing can be accomplished in a very shorttime.

An essential aspect of the present invention is the combined use ofaluminum and zirconium in a copper-nickel alloy containing 1 part nickelto about 10 parts copper. An alloy of this type without the aluminum orwithout the zirconium fails to develop the desired properties. Thecombination of these two elements, namely, aluminum and zirconium, isabsolutely essential and have what may be regarded as a synergisticeffect in the development of the high tensile strength and hardnesscomparable to or greater than that of copper-beryllium. Thus, typically,an alloy containing 90.0% copper, 9.0% nickel and 1.0% zirconium, but noaluminum, had an initial hardness of only 70 Vickers, which increased toonly 76 Vickers after ageing for 11 hours at 400 C. and to 79 Vickersafter ageing for 2 hours at 600 C. Similar results are obtained with analloy in which a similar percentage of aluminum is substituted for thezirconium. However, an alloy of 88.2% copper, 8.8% nickel, 1.0%zirconium and 2.0% aluminum had an initial hardness of Vickers after thesolution treatment which increased to 216 Vickers (96 Rockwell B) afterageing 11 hours at 400 C. and to 231 Vickers (98-99 Rockwell B) afterageing 2 hours at 600 C. An alloy containing the same amount of copperand nickel, but 0.5% zirconium and 2.5% aluminum had an initial hardnessof 111 Vickers after the solution treatment, which increased to 250Vickers Rockwell B) after ageing for 11 hours at 400 C. and to 265Vickers (2627 Rockwell C) after ageing for 2 hours at 600 C.

A preferred alloy in accordance with this invention is of the followingcompositions in percentages by weight:

Copper 83.4 Nickel 8.1

Aluminum 2.2

Zirconium 3 .8 Iron 1.0

Silicon 1.3

Carbon 0.1

This alloy, after casting and heating to 960 C. followed by quenching inwater, showed a tensile strength of about 60,000 pounds per square inchand a hardness of 69 Rockwell B. When given a further treatment for onlyone hour at 500 C. followed by quenching in water, the tensile strengthincreased to 113,000 pounds per square inch and the hardness to 93Rockwell B. It was found that the tensile strength and hardness could befurther increased by cold working or additional precipitation ageing orboth. For example, 50% cold working increased the tensile strength from113,000 pounds per square inch to 186,000 pounds per square inch and thehardness was well above 93 Rockwell B. This tensile strength iscomparable to the usual copper-beryllium alloys. An additional heattreatment for two hours at a temperature of 450 C. followed by quenchingin water, increased the tensile strength still further to 195,000 poundsper square inch.

An alloy of the same preferred composition, following the solutiontreatment, had its tensile strength increased from 60,000 to 125,000pounds per square inch after 25% cold working and to 142,000 pounds persquare inch after 50% cold working.

The same preferred alloy, following the solution treatment, when agehardened for only 15 minutes at a temperature of 565 C. and quenched inwater, had its tensile strength increased from 60,000 to 144,000 poundsper square inch and its hardness from 69 Rockwell B to 100 Rockwell B.When further treated by working to 25% reduction, the tensile strengthrose even further to 156,000 pounds per square inch and when worked to a50% reduction, the tensile strength rose to 162,000 pounds per squareinch.

I claim:

1. An alloy consisting essentially, by weight, of 82.2 to 89.1% copper,7.5 to 8.9% nickel, 0.8 to 3.47% aluminum and .05 to 4.0% zirconium.

2. An alloy as defined by claim 1 having also 1.0 to 1.6% silicon, 0.7to 1.3% iron and 0.05 to 0.5% carbon.

3. An alloy as defined by claim 1 which has been subjected to agehardening at least once at a temperature in the range of 400 to 600 C.for a period in the range of 15 minutes to 2 hours.

4. An alloy as defined by claim 1 which has been subjected to coldworking.

5. An alloy consisting essentially of, by weight, 83.4% copper, 8.1%nickel, 2.2% aluminum and 3.8% zirconium.

6. An alloys as defined by claim 5 having also about 1.0% iron, 1.3%silicon and 0.1% carbon.

References Cited in the file of this patent UNITED STATES PATENTS2,027,750 Munson Jan. 14, 1936 2,102,238 Pilling et al. Dec. 14, 19372,137,282 Hensel et al Nov. 22, 1938 2,143,914 Hensel et al. Jan. 17,1939 2,430,306 Smith Nov. 4, 1947

1. AN ALLOY CONSISTING ESSENTIALLY, BY WEIGHT, OF 82.2 TO 89.1% COPPER,7.5 TO 8.9% NICKEL, 0.8 TO 3.4% ALUMINUM AND .05 TO 4.0% ZIRCONIUM.